Some theories that attempt to explain why the big bang occurred include string cosmology, the ekpyrotic Universe model, the cyclic Universe model, the black hole theory, etc. All these theories are, unfortunately, unsatisfactory. After all, we certainly have no evidence for what might have happened before the Big Bang took place. However, there is one theory that I would like to discuss in the following paragraphs—the Hawking-Turok Instanton Theory.
This theory is actually a combination of two separate lines of research. In one, James Hartle and Stephen Hawking proposed a theory based the idea that the Universe did not have a boundary; in the other, Neil Turok worked with Martin Bucher and Alfred Goldhaber in creating an inflationary, open Universe theory. Eventually, they combined the two theories to create the Hawking-Turok Instanton Theory. In essence, Hawking and Turok believe that the Universe began from nothingness! Our open, inflationary Universe was formed from an “instanton”—a theoretical particle combining space and time. Consider a small, dimpled spherical volume that looks like
More importantly, a tremendous value of the Hawking-Turok Instanton Theory is that it combines quantum physics with what we observe, although many questions still remain unanswered. And after all, the Hawking-Turok Instanton Theory is just one possible explanation amongst many others. We ought to keep researching and working on discovering the truth behind the creation of our Universe.